The present invention relates to methods and apparatus for controlling the pressure around and above a substrate. More particularly, the present invention relates to improved wafer area pressure control rings.
In the fabrication of semiconductor-based devices (e.g., integrated circuits), layers of material may alternately be deposited onto and etched from a substrate (e.g., the semiconductor wafer). As is well known in the art, the etching of the deposited layers may be accomplished by a variety of techniques, including plasma-enhanced etching. In plasma-enhanced etching, the actual etching of the substrate takes place inside a plasma processing chamber. During etching, a plasma is formed from a suitable etchant source gas to etch areas of the substrate that are unprotected by the mask, leaving behind the desired pattern.
Among different types of plasma etching systems, those utilizing confinement rings have proven to be highly suitable for the efficient production of and/or for forming the ever shrinking features on the substrate. An example of such a system may be found in the commonly assigned U.S. Pat. No. 5,534,751, which is incorporated by reference herein. Although the use of confinement rings results in a significant improvement in the performance of plasma processing systems, current implementations can be improved. In particular, it is realized that improvements can be made in the way in which confinement rings are maintained and replaced. More particularly, significant improvements can be made in the way in which these rings are attached within the chamber.
Generally speaking, the confinement ring assembly includes a plurality of confinement rings, with the uppermost ring being the thickest and functioning as the attachment structure for attaching the confinement ring assembly to the a plunger. In the exemplary Exelan 2300 ™ plasma etching system, which is available from Lam Research Corporation of Fremont, Calif., the movement of the plunger moves the confinement ring assembly into position for processing or away from the plasma generating region to facilitate substrate insertion and removal. For example, as the plunger moves upward, the confinement ring assembly, including the uppermost ring and other rings of the assembly, moves upward to facilitate substrate insertion and removal. As the plunger assembly moves downward, the confinement rings of the assembly are positioned in place to facilitate processing.
In the past, a staircase hanger has been employed to couple the confinement rings of the confinement ring assembly together. With the confinement rings of the assembly coupled together via the staircase hanger, the entire assembly can then be coupled to the plunger by coupling the uppermost ring of the confinement ring assembly with the plunger. The aforementioned U.S. patent application Ser. No. 09/916,784 describes a twist-n-lock arrangement for coupling the confinement ring assembly with the plunger.
To facilitate discussion, FIG. 1A shows an exploded view of confinement ring assembly 102, including staircase hanger 104 and rings 106, 108, 110, and 112. Staircase hanger 104 is shown in greater detail in FIG. 1B. To simplify the illustration, only one staircase hanger and its associated hanger holes in the rings are shown. It should be noted that the confinement ring assembly typically includes a plurality of hangers and associated hanger holes (e.g., generally three sets of hangers and associated hanger holes) to provide adequate support for the confinement ring assembly.
Staircase hanger 104 includes a plurality of steps 154, 156, 158, and 160 for supporting respective rings 106, 108, 110, and 112. Each of rings 106, 108, 110, and 112 has an associated hanger hole to accommodate hanger 104. As shown in FIG. 1A, ring 112 has a hanger hole 120, ring 110 has a hanger hole 122, ring 108 has a hanger hole 124, and ring 106 has a hanger hole 126. The upper end of staircase hanger is coupled with top confinement ring 106 and hanger hole 126 via an appropriate fastening arrangement, such as a screw.
In the example of FIG. 1A, the hanger holes 120, 124, 126, and 128 have different sizes to facilitate the stowage and deployment of the confinement ring assembly. To stow the confinement ring assembly (e.g., during substrate insertion and removal), top confinement ring 106 are pulled upward by the upward movement of a plunger (not shown in FIG. 1A), which is connected to top confinement ring 106 via a keyhole 122. The hanger holes are dimensioned such that when the confinement rings are stowed, ring 112 rests on step 160 (see FIG. 1B), ring 110 rests on step 158, ring 108 rests on step 156, and ring 106 rests on step 154. As such, the entire assembly is moved upward and out of the path of substrate insertion and removal.
To deploy the confinement rings, the plunger is moved downward, which causes top confinement ring 106 and other confinement rings to move downward. When bottom confinement ring 112 makes contact with the lower electrode or another structure disposed below lower confinement ring 112, the movement of lower confinement ring is arrested. For example, the lower electrode may be disposed under lower confinement ring 112 and may make contact with an area 130 of the lower surface of lower confinement ring 112 as the entire confinement ring assembly moves downward. Even though the downward movement of lower confinement ring 112 is stopped, other rings of the confinement ring assembly, such as ring 110, 108, and 106 continue to move downward until their movement is arrested by lower confinement ring 112. As such, the rings collapse upon one another. A spacer button 132, which is disposed on the upper surface of each of confinement rings 112, 110, and 108 ensure that the rings are separated from one another by a predefined distance during processing.
Although the staircase hanger arrangement of FIG. 1A and FIG. 1B facilitate the deployment and stowage of the confinement ring assembly, improvements are possible. It has been noted that the use of staircase hanger 104 requires that hanger holes having different dimensions be provided in the confinement rings. With respect to FIG. 1A, for example, hanger holes 120, 122, and 124 need to have different sizes to facilitate the stowage and deployment of the confinement rings in the manner described above. This requirement means that confinement rings 112, 110, and 108 are different parts, requiring the manufacturer and/or users of the plasma processing system to stock different confinement rings for maintenance and repair. Furthermore, spacer buttons 132 must also be stocked. Additionally, some users report that the small size of spacer buttons 132 present difficulties during confinement ring maintenance in that it is easy to lose the small spacer button, or worse, to drop the spacer button in difficult-to-reach recesses within the plasma processing chamber.